Train control system



May 3, 1932.

A. G. WI LLl AMSON 1,856,822

TRAIN CONTROL SYSTEM Original Filed Nov. 10. 1 926 P1075 ramPz-wi awwemtoz Patented May 3, 1932 UNITED STATES PATENT OFFICE ABBA G. WILLIAMSON, OF CARNEGIE, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A. CORPORATION OF PENNSYLVANIA TRAIN common SYSTEM Original application filed November 10, 1926, Serial No. 147,403. Divided and this application filed November 14, 1930.

The present invention relates to train control systems, the train or traflic controlling means being of any suitable character such as signals or retarding or stopping devices or both, and has for its main object and feature the employment of an electron discharge device in which the phenomenon of secondary emission is utilized for train control purposes.

This application is a division of application Ser. N 0. 147,403, filed November 10, 1926.

In the accompanying drawings the invention is disclosed, by way of illustration but not of limitation, in a concrete and preferred form of which Fig. 1 is a diagrammatic View of a track circuit that may be employed in connection with the invention;

Fig. 2-is a diagrammatic view of a traincarried equipment disclosing one form of the invention; and r Fig. 3 is a graph showing certain operating characteristics of an electron tube .util izing the phenomenon of secondary emission.

Carried on the train is a pick-up coil indicated by the reference character 1. This pick-up coil 1 is suitably attached to the train in advance of the leading pair of wheels and axle of the train, and is suspended as close to the trackway induction element (here the running rails) as is practical.

A suitable trafiic governing translating device, under the control of the current induced in pick-up coil 1, is employed and is here indicated by direct-current polarized relay 24 which latter is biased, in any of the ways known in the art, as fully described and disclosed in applicationSer. No. 147,403, to assume one condition when direct current of an intermediate value, (say-a direct current of the average value of 0.40) is flowing in the coil .of the relay, and to assume a second condition when the current How is maintained at either an increased or decreased value with respectto said intermediate value. In the casehere illustrated, relay 24 is so biased that its polarized armature 257 assumes the right-hand position shown in Fig. 2, when the direct current flowing in the coil of relay 24 is of an intermediate value, and

Serial N0. 495,725.

assumes the left-hand position opposite to that shown in Fig. 2, when the direct current is maintained at either an increased or decreased value with respect to said intermediate value.

On the train there is provided a translating device as the medium through which the current induced in pick-up coil 1 effects a control over traffic-governing relay 24. This translating device, or electric detector, is electron discharge device E, having four elements, a plate P, a grid G, a filament F, and an element which we shall term anode A. The pick-up, or receiving, circuit includes pick-up coil 1, a blocking condenser 7, grid G, filament F, and connecting wires. A tuning condenser 222 spans the terminals of coil lto tune the circuit to resonance at the frequency of the track circuit current. The plate circuit is as follows: from direct current generator G resistance 253 to adjustable contact TC, then to coil of relay 24, wire 254, plate P, filament F, and wires 255 and 256 back to generator G Filament F is heated by the small battery 261 as shown. The circuit to the fourth element, anode A, is as follows: A, filament F, and wires 255 and 256 back to generator G The circuit through the indicating, or brake controlling magnet 33 is as follows: generator G resistance 253, adjustable contact TC, armature 257, wire 258,

coil of magnet 33, and wires 259, 260 and 256 use of the phenomenon of secondary emis-' sion. If an electron from filament F.) traveling at high speed collides with a metallic surface such as plate P, the giving up of the energy at said surface is likely to j ar other electrons out of the surface at the point where the collision occurs. This emission of the electron from the surface, caused by the colliding electrons, is called secondary emission, and the number of electrons so emitted depends upon the speed of thecolliding electrons-it may be none at all or it may be as many as a dozen or more. Qrdinarily the generator G wire 262, anode will at once reenter the surface from which ,Inediate value,. wi-ll.movearmature-257 to they were emitted, but, if there is, in the vicinity of said surface, an electrode such as anode A of high potential, the secondary electrons will not reenter the surface (plate P) from which they camebut will go to the high potential electrode (anode A thereby causing a secondary electron flow from the surface toward which the first electron flow occurred. Ihus when fi'l'ament'F" is heated primary electronswill be emitted therefrom, and these electrons will pass, some to posi-. tive anode A and some to positive plate P, and it At has a. higher potential than'P, secondary emission from plate. P- to anode A will be the result.

- In- Fig. 3 is shown a-characteristic curve of. a tube of this type, for a given potential of anode A. In said Fig. 3 thehorizontal axis represents. the voltage-of the plate with. respect to the filament, and the vertical axis represents the current flowing in the plate circuit. Front this curve it will be seen that the-plate cue-rent, for a given potential of anode A, atofirst increases-with the plate voltage, but. that, after thevalue of the plate voltage reaches the point designated by point A0, the platev circuit currentdecreases as the plate voltageincreases-in fact becomes zero at the plate voltage designated by point B0.

Let-us assume tlrat,.in the construction of Fig.2, the voltages-oi the anodeand plate are so adjzustedeby contact TC that tube: E is operating atzpointBoon; the curveof Fig. 8. In other words: the primary a-ndsecondary emission is substantially equally powerful; and the value of the-plate circuit current is substantially zero. When: current is induced coil 1, by current flow in the traclcway equipment, grid G- will be rendered negative with. respect to filament'F, and this will aaiect the prim-aryemiss-ionof electrons from-l, but it will also affect, and to a greater extent, secondary emission of electrons from P to. A. Thus the two electron streamswill beunbalanced tosuch an extent that a currentfi-ow of intermediate value will take place in'tli'eplate. circuit; Relay 24, being biased in the manner previouslyinhand. position and 'thecircuit through 1nag-.

Likew1se,if the net' 33 will be ruptured. anode circuit should be ruptured or so. aftected that thepotentia]. oflsaid anode is no longer. greater than. that of the plate, no:

secondary em-i ssion will take place and the full value of the current supplied by generator G will flow inthe plate-circuit, which current Value, being greater than the :interits left-hand position and thus open the circuit through 33.

In Fig. 1 is shown a suitable trackway equipmentto cooperate with the train-carried equipment above described. As shown in Fig. 1, 55- and 56 represent the twotrafiic rails arranged into blocks A, B and C by means oi insulation 3.. The normal direction or" tra'h'ic through said blocks is indicated' by the arrow betweenthe rails. At the ingoing end of each block is a relay, marked 148 in block 0 and 148 in block B, connected across the rails by suitable leads, and at the outgoing end of each block is a track battery 158 which is connected across the rails. by leads: 150i and 156. The function of this battery is merely to; energize atrack. relay like 148"1t? is not sufiiciently powerful to control the train. The train con-- trol current isrhere' supplied from generator 51,. in this instance of the. alternating current type, by way ofline wires 52. andr53 to a track transformer associated with each block. Taking block B as an eXamplfe',.it will be seenthat. the primary of track transformer 101 is connected by wires 143 and. 144 to line wires-52 and 53. Secondary 145-otuthe track transformeris connected. to rail. 56 by'wi-re 146-, armature 147 (of the track: relay ot: the block in advance) contact 149 and wire 150, and is connected to rail 55: by wire 152-, resistance 153 and wires-1'54 and 156. Tlieifunction of resistance 153 is to prevent secondary 1.45 from: short circuiting the battery. An impedance coil 157 is interposed :in' wire 156 to choke back the flow of alternatingrcurrentv sethat it will not pass: to the battery. The-power supplied'from secondary145 to the rails is of such amplitudeasto: energize the. pick-up circuit on the train. It will. now be understood that the presence, in the rails. o fv current from 145 will choke down: the current inthe train-carried charged circuit so.

that it willhave the intermediate 1 21111601 0A0, and therefore the circuit under control of relay 24 will remain closed. I

If block C be unoccupied, hen track relay 148 will beenergized and train-control :cur

rent fromsetcondary 145 will pass to the rails" of block B, with the result that if a train enters block B from block A, suchtrain will have itscab equipment controlled thereby giving clear indication. On the other'hand,

if block C is occupied when a train-enters block B from A, then such train, entering block B from A, will receive no train-coir trol current because track relay 148' otibl'ock' C will have been deenergized by the train in:

block G thereby dropping armature 147 and opening the circuit from secondary 145 to:

rails. The effect of this condit-ionon the train is that no current will flow in the charged circuit passing through relay 24,. and that therefore the. circuit through 33 is ruptured.

It will further be observed that, although the presence of a train in block C deenergizes track relay 148 and thus cuts ofi train-control current from the rails of block B, track relay 148 of block B will nevertheless remain energized (provided B is unoccupied) by reason of current flow from battery 158 so that a train in block A will not be controlled by a train in block C.

If a train enters a block already occupied by another train, then the train so entering will be subject to no train-control current.

I claim:

1. A train control system including: a trackway circuit having a source of current, a train, a train-carried electron discharge device containing four elements, charged traincarried circuit means for maintaining two of said elements at a positive potential with respect to a third element, a train-carried receiving circuit, in an inductive relation with the trackway circuit and responsive to current flowing therein, to control the potential of the fourth element of said device with respect to the third element, whereby the flow of current in the circuit means of the first two-mentioned elements of said device is varied.

2. A train control system including: a trackway circuit having a source of current, a train, a train-carried electron discharge device containing plate, anode, filament and grid elements, charged train-carried circuit means for maintaining the plate and anode at a positive potential with respect to the filament, a train-carried receiving circuit, in an inductive relation with said trackway circuit and responsive to current flowing therein, to control the potential of the grid with respect to the filament, whereby the flow of current in the plate circuit is varied.

3. A train control system including: a track-way circuit having a source of current, a train-carried electron discharge device containing plate, anode, filament and grid elements, charged train-carried circuit means, to maintain the plate and anode at a positive potential with respect to the filament, a traincarried receiving circuit in an inductive relation with the trackway circuit and responsive to current flowing therein, to control the potential of the grid with respect to the filament, whereby a predetermined flow of direct current in the plate circuit is established in response to a flow of current in the track way circuit.

4. A train control system including: a trackway circuit having a source of current, a train-carried electron discharge device containing plate, anode, filament and grid elements, charged train-carried circuit means, to maintain the plate and anode at a positive potential with respect to the filament, a traincarried receiving circuit in an inductive relation with the trackway circuit and responsive to current flowing therein to maintain the grid at a negative potential with respect to the filament, whereby a predetermined flow of direct current in the plate circuit is established in response to a flow of current in the trackway circuit.

5. A train control system including: a trackway circuit having a source of current, a train, a train-carried electron discharge device containing plate, anode, filament and grid elements, charged train-carried circuit means, for maintaining the plate and anode at different positive potentials with respect to the filament, the anode having greater potential than the plate, and a train-carried receiving circuit in an inductive relation with the trackway circuit and responsive to current flowing therein, to control the potential of the grid with respect to the filament.

6. A train control system including: a trackway circuit having a source of current, a train, a train-carried electron discharge device having elements capable of primary and secondary electron emission, a train-carried circuit controlled by the relative amount of primary and secondary electron emission of the electron discharge device, and a traincarried circut, controlled by the trackway circuit to unequally vary the primary and secondary electron emission of the electron discharge device.

7. A train control system including: a train, a train-carried electron discharge device having elements capable of primary and secondary electron emission, a train-carried circuit controlled by the relative amount of primary and secondary emission of the electron discharge device, and a trackway circuit to unequally vary the primary and secondary electron emission of the electron discharge device.

8. A train control system 7 including: a trackway circuit having a source of current, a train, a train-carried electron discharge device having elements capable of primary and secondary electron emission, means on the train to control said primary and secondary electron emission, a train-carried circuit controlled by the relative amount of primary and secondary electron emission of the electron discharge device, and a train-carried circuit controlled by the trackway circuit to unequally vary the primary and secondary electron emission of the electron discharge device. 7

9. A train control system including: a trackway circuit having a source of current, a train, a train-carried electron discharge device having elements capable of primary and secondary electron emission, means on the train to substantially balance said primary and secondary electron emission, a train-carried circuit controlled by the relative amount of primary and secondary electron emission of the electron discharge device, and a traincarried circuit controlled by the trackway circuit to unbalance the primary and secondary electron emission of the electron discharge device.

10. A train control system including: a train, a train-carried electron discharge device having elements capable of primary and secondary electron emission, means on the train to control said primary and secondary electron emission, a train-carried circuit controlled by the relative amountof primary and secondary electron emission of the electron discharge device, and a trackway circuit to unequally vary the primary and secondary electron emission of the electron discharge device.

11. A train control system including: a train, a train-carried electron discharge device having elements capable of primary and secondary electron emission, means on the train to substantially balance said primary and secondary electron emission, a train-carried circuit controlled by the relative amount of primary and secondary electron emission of theelectron discharge device, and a track- Way circuit to unbalance the primary and secondary electron emission of the electron discharge device.

Signed'at-Svvissvale, in the county of Allegheny, and'State of Pennsylvania, this 13th day of November, 1930'.

ABBA G. WILLIAMSON. 

